Detection of artificial red colorants in saffron using UV-vis spectrometry and tristimulus colorimetry

UV-Vis spectrometry, including elaboration of the 1(st) and 2(nd) derivative, was employed for the detection of red colorants in saffron extracts prepared according to the ISO 3632 -1993 standard. The sensitivity of the method was improved when saffron naturally encountered colorants, the crocins, were removed from the analytical sample. For this reason, thermal treatment of the extract at low pH was necessary. In this way even low levels of artificial red colorants (30g /kg saffron powder) were detectable. Moreover, tristimulus colorimetry was used as a screening method to control the authenticity of saffron samples prior to sample pretreatment. It seems that the chromatic parameters a* and h offer some preliminary evidence as to whereas red colorants are present in a saffron aqueous extract.